Re: [PATCH] printk/kdb: Redirect printk messages into kdb in any context

From: Sergey Senozhatsky
Date: Thu Jun 11 2020 - 03:27:37 EST


On (20/06/10 17:41), Daniel Thompson wrote:
> > Thanks for the link. I'm slightly surprised it took so many years
> > to notice the addition of printk_nmi/printk_safe :)
>
> Rather by coincidence (at least I think its a coincidence) the problem
> has recently become much more obvious.
>
> 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()") just brought
> this to the surface by treating debug traps as NMIs. This means the CPU
> that takes a breakpoint, and where almost all of the kdb printk() calls
> take place, will now unconditionally have printk() interception enabled.

Interesting. Feels like ist_enter() should have been using
printk_nmi_enter/exit() in the first place.

-ss